This research proposes to define a unique biochemical abnormality in erythrocyte membrane spectrin that is characteristic of and specific to x-linked Duchenne muscular dystrophy. Using the abnormally increased (32P)-phosphorylation of erythrocyte protein band II as a marker, methods of peptide mapping and isolation are proposed that involve a number of peptide cleavage techniques. Methods of analysis include gel filtration, stacking polyacrylamide gel electrophoresis, and reverse phase high performance liquid chromatography. This proposal is the next phase of a long-term project to define the biochemical defect in Duchenne dystrophy, to determine the pathogenesis of the disease, and to use these data to develop diagnostic methods for patients, carriers, and fetuses at risk.